Hitches connecting the tongue of a trailer or farm implement such as a plow to the drawbar of a tractor or other vehicle are well known in the art. These hitches have a vertical hitch pin which allows relative pivotal motion between the tongue and drawbar. The pin is generally extended through apertures in both the drawbar and the tongue.
Various devices have been used to secure the pin in the hitch to protect against inadvertent uncoupling. For example, objects such as hair pin and cotter pin retainers have been mounted on the pin end opposite its head to prevent withdrawal of the pin through the apertures. However, such retainers are awkward to use, are easily lost, and can be jerked out by crop stubble, dirt ridges, vibrations, etc. Threaded nuts have also been used but they too are awkward, easily lost, and can be spun off by vibrations, crop stubble, etc.
Various devices have also been used which block the head of the pin so as to prevent it from retracting out of the hitch. However, these blocking devices move between an open position which allows a pin to be inserted or withdrawn and a closed position which blocks the pin from being removed. The devices stay in whatever position they are placed, whether open or closed. Therefore, when such a device encounters a force during use which causes it to open, it will stay open until manually or accidentally corrected, and until corrected will not serve its intended function of locking the hitch pin in place. Devices of this type are shown, for example, in U.S. Pat. Nos. 1,419,398, 2,397,964, 2,593,247, 2,697,618, 3,779,653, 3,794,357 and 4,394,031.
U.S. Pat. No. 3,479,057 discloses a safety device for a trailer hitch in which an arm is suspended over a ball and socket hitch to keep the two secured together. The arm must be pushed down in order to pivot it away from the socket. This is difficult to do manually. Further, the downward force which would open this safety device is the most likely force to be encountered in the field. If any object were to rest on the arm so as to have its weight supported thereby, the arm would be naturally pivoted toward opening.
The present invention is directed toward overcoming one or more of the problems as set forth above.